A digital content such as a musical content is different from the conventional content in that the digital content can be copied a plurality of times without deterioration of its quality. For this reason, in recent years, the number of illegal acts such as acts distributing and exchanging contents without permissions given by the authors of the contents have been increasing in accordance with popularization of the Internet, increasing speeds of apparatus such as PCs (Personal Computers) and rising capacities of storage devices.
In order to prevent these illegal acts, efforts are made to popularize a copyright management system utilizing a DRM (Digital Rights Management) technology imposing limitations on distributions and utilizations of contents. In the copyright management system, as proposed in an SDMI (Secure Digital Music Initiative) and the like, it is general that the copyright of a content is managed in accordance with a method (referred to hereafter as a check-in/check-out method). In the method, utilization (reproduction and copying) of a content is limited on the basis of usage rule information described in a license (right information).
As for the content reproduction apparatus, a PD (Portable Device) having excellent portability has been becoming popular. In a PD conforming to the conventional SDMI, only copyright management is performed as follows. The reproduction of the content is controlled based on a license, which is attached to the content, checked out from a PC or the like in accordance with the check-in/check-out method cited above. For more information, refer to Japanese Patent Laid-open No. 2002-312211.